Mercurial repo too large, can't connect, clone

Our BitBucket repo has grown to over 3 gigs and now when I try to clone in SourceTree all I get is the trying to connect symbol. When I try in Tortoise it clones to a certain point then disconnects saying it expected # bytes but got #.

I can't download the .zip from BitBucket because it's too large. What can I do to clone?